[clangd] Add xrefs LSP boilerplate implementation.

Reviewers: ilya-biryukov, ioeric

Subscribers: MaskRay, jkorous, arphaman, cfe-commits

Differential Revision: https://reviews.llvm.org/D50896

llvm-svn: 341462
diff --git a/clang-tools-extra/clangd/Protocol.cpp b/clang-tools-extra/clangd/Protocol.cpp
index 609cfa6..4209379 100644
--- a/clang-tools-extra/clangd/Protocol.cpp
+++ b/clang-tools-extra/clangd/Protocol.cpp
@@ -616,6 +616,11 @@
          O.map("compilationDatabaseChanges", CCPC.compilationDatabaseChanges);
 }
 
+bool fromJSON(const json::Value &Params, ReferenceParams &R) {
+  TextDocumentPositionParams &Base = R;
+  return fromJSON(Params, Base);
+}
+
 json::Value toJSON(const CancelParams &CP) {
   return json::Object{{"id", CP.ID}};
 }